Fluid actuator

ABSTRACT

A fluid actuator applicable to high load with small space, comprising a core with an output shaft and two discs; and a cylinder casing which receives the core in a hollow, an upper end of the upper shaft projecting out of an upper opening and the core is set free. The cylinder casing includes an annular protrusion projecting into an air gap between the discs, wherein a small seal member which seals upper and lower spaces is provided between a portion of the core located between the discs and an annular protrusion and a large seal member which seals upper and lower spaces is provided between an inner peripheral surface of the cylinder casing, and an outer peripheral surface of the discs. The interior of the cylinder casing is divided into four small cavities abutting on one another vertically and an effective pressure-receiving area of the large seal member is larger than that of the small seal member to each of the small cavities.

TECHNICAL FIELD

The present invention relates to a fluid actuator suitable for use invibration removing of high precision measuring apparatus andsemiconductor manufacturing apparatus, for example.

BACKGROUND ART

Conventionally, fluid actuators, such as air spring, air cylinder, andhydraulic cylinder, have been well known. In such fluid actuators, whileon one hand a supporting load or operating force by the fluid actuatoris determined by internal pressure and effective pressure-receivingarea, on the other hand the pressure of the fluid to be supplied islimited. Therefore, in order to make it possible to use the fluidactuator in a high load application, there is no other way thanenlarging the effective pressure-receiving area.

For example, JP B H7-76576 (examined) and JP A H3-219141(unexamined)disclose apparatuses in which an air spring is used for suppressingvibration. In order to enlarge the force of such air springs, it isnecessary to increase the number of air springs.

In the field of precision working, in order to suppress a rise in thecost for maintaining clean environment, it is required that theequipment be made more intensive without exerting bad influence uponprecision working. On the other hand, there are demands for larger sizeand higher speed of the equipment, and this makes it more and morenecessary to improve the support capability per unit area andcontrolling force with respect to the equipment. That is, it is requiredthat a large controlling force be generated in a small space andvibration controllability be improved in a wide frequency range. Thisposes a problem that it is not possible to increase the number of fluidactuators, and to enlarge the effective pressure-receiving area.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a fluid actuator whicheliminates the foregoing problem and which can be applied to high loadswith small space.

In order to achieve the above object, according to the presentinvention, there is provided a fluid actuator comprising: a core havinga plurality of discs protruding around an output shaft; a cylindercasing which has a body of hollow configuration with an opening providedat its upper portion, and which receives the core in the hollow body ina state where not only an upper end of the output shaft is projected outof the opening but a lower portion of the core is set free, and whichhas an annular protrusion projecting into an air gap between the discs;an annular small seal member interposed between a portion of the corelocated between the discs and the annular protrusion so as to allowtheir relative movement in upward and downward directions and so as topartition upper and lower cavities from one to the other; and an annularlarge seal member interposed between an inner peripheral surface of thecylinder casing and outer periphery portion of the discs so as to allowtheir relative movement in upward and downward directions and so as topartition upper and lower cavities from each other, wherein a pluralityof small cavities are defined by being partitioned by the small sealmember and the large seal member so as to be arrayed vertically, one ofa first group of the small cavities in odd-numbered stages counted froma bottom and a second group of the small cavities in even-numberedstages counted from the bottom communicate with the atmosphere and theother of the first group and the second group communicate with oneanother, at least one small cavity of the other of the first group andthe second group communicates with a fluid flow passage for supplyingand discharging pressurized fluid, and an effective pressure-receivingarea on the large seal member side is larger than an effectivepressure-receiving area on the small seal member side in each of thesmall cavities.

Further, according to the present invention, there is provided a fluidactuator comprising: a core having a plurality of discs protrudingaround an output shaft; a cylinder casing which has a body of hollowconfiguration with an opening provided at its upper portion, and whichreceives the core in the hollow body in a state where not only an upperend of the output shaft is projected out of the opening but a lowerportion of the core is set free, and which has an annular protrusionprojecting into an air gap between the discs; an annular small sealmember interposed between a portion of the core located between thediscs and the annular protrusion so as to allow their relative movementin upward and downward directions and so as to partition upper and lowercavities from one to the other; and an annular large seal memberinterposed between an inner peripheral surface of the cylinder casingand an outer periphery portion of the discs so as to allow theirrelative movement in upward and downward directions and so as topartition upper and lower cavities from each other, wherein a pluralityof small cavities are defined by being partitioned by the small sealmember and the large seal member so as to be arrayed vertically, a firstgroup of the small cavities in odd-numbered stages counted from a bottomcommunicate with one another, at least one small cavity in the firstgroup communicating with a first fluid flow passage for supplying anddischarging pressurized fluid, a second group of the small cavities ineven-numbered stages counted from the bottom communicate with oneanother, at least one small cavity in the second group communicatingwith a second fluid flow passage for supplying and dischargingpressurized fluid, and an effective pressure-receiving area on the largeseal member side is larger than an effective pressure-receiving area onthe small seal member side in each of the small cavities.

Furthermore, according to the present invention, there is provided afluid actuator comprising: a cylinder casing opened at its upperportion; a core disposed inside the cylinder casing; a small seal memberwhich is interposed between the cylinder casing and the core and whichdoes not interfere with upward and downward relative movement of thecylinder casing and the core; a large seal member which is interposed inalternate relation with the small seal member between the core and thecylinder casing and which does not interfere with upward and downwardrelative movement of the core and the cylinder casing, and further whichhas an effective pressure-receiving area larger than that of the smallseal member; a fluid flow passage for supplying pressurized fluid to asmall cavity defined by the small seal member and the large seal memberin odd-numbered stage counted from a bottom, and for discharging thefluid present in the small cavity; and an opening which allows a smallcavity defined by the small seal member and the large seal member ineven-numbered stage counted from the bottom to communicate with theatmosphere.

Still furthermore, according to the present invention, there is provideda fluid actuator comprising: a cylinder casing opened at its upperportion; a core disposed inside the cylinder casing; a small seal memberwhich is interposed between the cylinder casing and the core and whichdoes not interfere with upward and downward relative movement of thecylinder casing and the core; a large seal member which is interposed inalternate relation with the small seal member between the core and thecylinder casing and which does not interfere with upward and downwardrelative movement of the core and the cylinder casing, and further whichhas an effective pressure-receiving area larger than that of the smallseal member; an opening which allows a first fluid flow passage tocommunicate with the atmosphere, the first fluid flow passage servingfor supplying pressurized fluid into a small cavity defined by the smallseal member and the large seal member in odd-numbered stage counted froma bottom, and for discharging the fluid in this small cavity; and asecond fluid flow passage for supplying pressurized fluid to a smallcavity defined by the small seal member and the large seal member ineven-numbered stage counted from the bottom, and for discharging thefluid in this small cavity.

Still furthermore, according to the present invention, there is provideda fluid actuator comprising: a cylinder casing opened at its upper andlower portions; a core disposed inside the cylinder casing; a small sealmember which is interposed between the cylinder casing and the core andwhich does not interfere with upward and downward relative movement ofthe cylinder casing and the core; a large seal member which isinterposed between the core and the cylinder casing and which does notinterfere with upward and downward relative movement of the core and thecylinder casing, and further which has an effective pressure-receivingarea larger than that of the small seal member; and a fluid flow passagefor supplying pressurized fluid to a small cavity defined by the smallseal member and the large seal member and for discharging the fluid inthis small cavity.

Still furthermore, according to the present invention, there is provideda fluid actuator comprising: a cylinder casing opened at its upper andlower portions; a core disposed inside the cylinder casing; a small sealmember which is interposed between the cylinder casing and the core andwhich does not interfere with upward and downward relative movement ofthe cylinder casing and the core; a large seal member which isinterposed in alternate relation with the small seal member between thecore and the cylinder casing and which does not interfere with upwardand downward relative movement of the core and the cylinder casing, andfurther which has an effective pressure-receiving area larger than thatof the small seal member; a fluid flow passage for supplying pressurizedfluid to a small cavity defined by the small seal member and the largeseal member in one of odd-numbered stage and even-numbered stage countedfrom a bottom, and for discharging the fluid in this small cavity; andan opening which allows a small cavity, defined by the small seal memberand the large seal member in the other of the odd-numbered stage and theeven-numbered stage, to communicate with the atmosphere.

Still furthermore, according to the present invention, there is provideda fluid actuator comprising: a cylinder casing opened at its upper andlower portions; a core disposed inside the cylinder casing; a small sealmember which is interposed between the cylinder casing and the core andwhich does not interfere with upward and downward relative movement ofthe cylinder casing and the core; a large seal member which isinterposed in alternate relation with the small seal member between thecore and the cylinder casing and which does not interfere with upwardand downward relative movement of the core and the cylinder casing, andfurther which has an effective pressure-receiving area larger than thatof the small seal member; a first fluid flow passage for supplyingpressurized fluid to a small cavity defined by the small seal member andthe large seal member in one of odd-numbered stage and even-numberedstage counted from a bottom, and for discharging the fluid in this smallcavity; and a second fluid flow passage for supplying pressurized fluidto a small cavity defined by the small seal member and the large sealmember in the other of the odd-numbered stage and even-numbered stage,and for discharging the fluid in this small cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a fluid actuator according to a firstembodiment of the present invention.

FIG. 2 is a sectional view of a fluid actuator according to a secondembodiment of the present invention.

FIG. 3 is a sectional view of a fluid actuator according to a thirdembodiment of the present invention.

FIG. 4 is a sectional view of a fluid actuator according to a fourthembodiment of the present invention.

FIG. 5 is a sectional view of a fluid actuator according to a fifthembodiment of the present invention.

FIG. 6 is a sectional view of a fluid actuator according to a sixthembodiment of the present invention.

FIG. 7 shows an example of application of the fluid actuator shown inFIG. 1.

FIG. 8 shows an example of application of the fluid actuator shown inFIG. 2.

FIG. 9 shows an example of application of a hybrid actuator using thefluid actuator shown in FIG. 1.

FIG. 10 shows an example of application of a hybrid actuator using thefluid actuator shown in FIG. 2.

FIG. 11 shows an example of application of a hybrid actuator using afluid actuator substantially identical with the fluid actuator shown inFIG. 1.

FIG. 12 shows an example of application of another hybrid actuator usingthe fluid actuator shown in FIG. 11.

FIG. 13 shows an example of application of further another hybridactuator using the fluid actuator shown in FIG. 11.

FIG. 14 shows an example of application of still further another hybridactuator using the fluid actuator shown in FIG. 11.

FIG. 15 shows an example of application of a hybrid actuator using afluid actuator analogous to the fluid actuator shown in FIG. 3.

FIG. 16 shows an example of application of another hybrid actuator usingthe fluid actuator shown in FIG. 15.

FIG. 17 shows an example of application of further another hybridactuator using the fluid actuator shown in FIG. 15.

FIG. 18 shows an example of application of still further another hybridactuator using the fluid actuator shown in FIG. 15.

FIG. 19 shows an example of application of a hybrid actuator using afluid actuator according to a seventh embodiment of the presentinvention.

FIG. 20 shows an example of application of a hybrid actuator using afluid actuator according to an eighth embodiment of the presentinvention.

FIG. 21 shows an example of application of a hybrid actuator using afluid actuator according to a ninth embodiment of the present invention.

FIG. 22 shows an example of application of a hybrid actuator using afluid actuator according to a tenth embodiment of the present invention.

FIG. 23 shows an example of application of a hybrid actuator using afluid actuator according to an eleventh embodiment of the presentinvention.

FIG. 24 shows an example of application of a hybrid actuator using afluid actuator according to a twelfth embodiment of the presentinvention.

FIG. 25 shows an example of application of a hybrid actuator using thefluid actuator shown in FIG. 19.

FIG. 26 shows an example of application of another hybrid actuator usingthe fluid actuator shown in FIG. 19.

FIG. 27 shows an example of application of a further hybrid actuatorusing the fluid actuator shown in FIG. 19.

FIG. 28 shows an example of application of a hybrid actuator using afluid actuator according to a thirteenth embodiment of the presentinvention.

FIG. 29 shows an example of application of a hybrid actuator using afluid actuator according to a fourteenth embodiment of the presentinvention.

FIG. 30 shows an example of application of a hybrid actuator using afluid actuator according to a fifteenth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are described below with referenceto the accompanying drawings.

FIG. 1 shows a fluid actuator 1A according to a first embodiment of thepresent invention. The fluid actuator 1A comprises a core 13 having twodiscs 12 protruding from an outer periphery of an output shaft 11, and acylinder casing 16 which has a hollow configuration with an opening 14provided in its upper portion, and which receives the core 13 within thehollow body in a state where a lower portion of the core 13 is set free,and further which has an annular protrusion 15 projecting into an airgap between the discs 12, 12.

Between a portion of the core 13 positioned between the discs 12, 12 andthe annular protrusion 15, a small diaphragm 17 is interposed forallowing upward and downward relative movement between the core 13 andthe annular protrusion 15 and for partitioning upper and lower cavities.Between the inner peripheral surface of the cylinder casing 16 and theouter peripheral portion of disc 12, a large diaphragm 18 is interposed,for allowing upward and downward relative movement between the cylindercasing 16 and the discs 12 and for partitioning upper and lowercavities. By this arrangement, the cavity within the cylinder casing 16is partitioned into four vertically abutting small cavities 19.Meanwhile, in the small cavities 19, an effective pressure-receivingarea on the large diaphragm 18 side is larger than an effectivepressure-receiving area on the small diaphragm 17 side. The smalldiaphragm 17 and large diaphragm 18 are comprised of a member which hasa sealing capability and enables relative displacement of an innerperiphery side member and an outer periphery side member. It followsfrom the above that the diaphragms 17, 19 allow for friction-lessrelative movement of the parts.

Small cavities 19 in odd-numbered stages counted from a bottom of thecylinder casing 16, that is, in the first and third stages counted fromthe bottom communicate with each other. There are various methods ofcommunication, which are not limitative. In the embodiments shownherein, the small cavities 19, 19 in the first and third stagescommunicate with each other by means of a through hole 20 bored in theoutput shaft 11. Preferably, this through hole 20 has as large a crosssection as possible in order to reduce the fluid friction. Further, thesmall cavity 19 in the first stage is connected to a fluid flow passage21 for supplying and discharging a pressurized fluid, while the smallcavities 19, 19 in the first and third stages are arranged in series.

On the other hand, small cavities 19 in even-numbered stages countedfrom the bottom of the cylinder casing 16, that is, the in the secondstage counted from the bottom communicate with the atmosphere. Morespecifically, the small cavity 19 in the second stage communicates withthe atmosphere by means of a through hole 22 bored in a side wall of thecylinder casing 16.

On the fluid flow passage 21, a control valve 23 for controlling thefluid flow is provided, and the fluid actuator 1A is controlled by thiscontrol valve 23. As to this fluid, for example, oil as well as gasessuch as air, nitrogen, carbon dioxide and helium are preferable.

In addition, the fluid flow passage 21 may communicate with the smallcavity 19 in the third stage instead of the small cavity 19 in firststage.

With this arrangement, since each of the small cavities 19 in theeven-numbered stage counted from the bottom of the cylinder casing 16,functions as single fluid actuators independent of one another, thefluid actuator 1A occupies an installation area of a single conventionalfluid actuator such as a single air spring or air cylinder or hydrauliccylinder corresponding to one small cavity 19 and has a capability equalto a sum of capabilities of the two conventional fluid actuators.Accordingly, by such an arrangement, it becomes possible to apply thefluid actuator 1A to high load applications with small installationspace.

FIG. 2 shows a fluid actuator 1B according to a second embodiment of thepresent invention, where parts common to the foregoing fluid actuator 1Aare designated by the same reference numerals and their description isomitted.

This fluid actuator 1B, basically, differs from the fluid actuator 1Ashown in FIG. 1 only in the number of the small cavities 19 andotherwise substantially identical in structure. More specifically, thefluid actuator 1B is so structured that six small cavities 19 are placedwithin the cylinder casing 16 so as to be vertically adjacent to oneanother. The small cavities 19 in even-numbered stages counted from thebottom of the cylinder casing 16 communicate with one another by meansof a through hole 20 formed in the output shaft 11. Further, a fluidflow passage 21 is connected to the small cavity 19 in a third stagecounted from the bottom, so as to communicate therewith, while the smallcavities 19 in the first, third and fifth stages are arranged in series.

Thus, by increasing the number of small cavities 19, the fluid actuator1B has a capability equal to a sum of the capabilities of conventionalfluid actuators, each of which corresponds to each of the small cavities19 in the even-numbered stages counted from the bottom, that is, acapability equal to a sum of three fluid actuators' capabilities, andyet only requires an installation area identical to the installationarea necessary for a single conventional fluid actuator corresponding toone small cavity 19.

In addition, the present invention also includes a fluid actuator inwhich the small cavities 19 where the pressurized fluid flows in and outare arranged not only in series so as to communicate with one anothervia the through hole 20 as described above, but also in parallel so asto communicate directly with the fluid flow passage 21.

Furthermore, in the above embodiments, the small cavities 19 arearranged in parallel so as to communicate directly with the atmosphere.However, the present invention also includes a fluid actuator in whichthe small cavities 19 are arranged in series so as to communicate withthe atmosphere via other small cavities 19.

FIG. 3 shows a fluid actuator 2A according to a third embodiment of thepresent invention, where parts common to the foregoing fluid actuatorare designated by the same reference numerals and their description isomitted.

This fluid actuator 2A has a cylinder casing 31 instead of the cylindercasing 16 of the above-described embodiments. The small cavities 19within the cylinder casing 31 do not communicate with the atmosphere,and the uppermost small cavity 19 is shut off from outside by the smallseal member 17.

The small cavities 19 in odd-numbered stages counted from the bottom ofthe cylinder casing 31 communicate with one another by means of athrough hole 20 formed in the output shaft 11. Further, a first fluidflow passage 21 a for supplying and discharging a pressurized fluid isconnected to the small cavities 19 in third-numbered stage counted fromthe bottom, so as to communicate therewith.

On the other hand, the small cavities 19 in even-numbered stages countedfrom the bottom of the cylinder casing 31 communicate with one anotherby means of a through hole 32 formed in a side wall of the cylindercasing 31. Further, this through hole 32 is connected to a second fluidflow passage 21 b which supplies and discharges a pressurized fluid,while the small cavities 19 in even-numbered stages counted from thebottom are arranged in parallel.

A pressure of the fluid supplied from each of the first fluid flowpassage 21 a and the second fluid flow passage 21 b contains a staticpressure component and a dynamic pressure component. In the case wherethe dynamic pressure components of the first fluid flow passage 21 a andthe second fluid flow passage 21 b are in opposite phase to each other,a force due to the fluid pressure of the first fluid flow passage 21 aand a force due to the fluid pressure of the second fluid flow passage21 b are summed up, and the summed-up force acts on the output shaft 11.Conversely, in the case where the dynamic pressure components of thefirst fluid flow passage 21 a and the second fluid flow passage 21 b arein phase with each other, a force due to the fluid pressure of the firstfluid flow passage 21 a and a force due to the fluid pressure of thesecond fluid flow passage 21 b cancel each other, and a force remainingas a difference between the two forces acts on the output shaft 11.Therefore, in the fluid actuator 2A using the first fluid flow passage21 a and the second fluid flow passage 21 b, the output shaft 11 can beheld in a position where forces due to the pressures of the first fluidflow passage 21 a and the second fluid flow passage 21 b, respectively,are balanced, and besides, forces due to static pressure components ofthe first fluid flow passage 21 a and the second fluid flow passage 21b, respectively, cancel each other so that only their respective dynamicpressure components can act on a driven member.

In addition, also in this fluid actuator 2A, the necessary installationarea is the same as the aforementioned installation area required for asingle conventional fluid actuator corresponding to one small cavity 19.

FIG. 4 shows a fluid actuator 2B according to a fourth embodiment of thepresent invention, where parts common to the foregoing fluid actuatorare designated by the same reference numerals and their description isomitted.

In this fluid actuator 2B, the small cavities 19 in odd-numbered stagescounted from the bottom of the cylinder casing 31 communicate with oneanother by means of a through hole 33 formed in a wall portion of thecylinder casing 31. Except that the through hole 33 is provided insteadof the through hole 20, the fluid actuator 2B is substantially the sameas the fluid actuator 2A. In this fluid actuator 2B, not only the smallcavities 19 in even-numbered stages counted from the bottom but also thesmall cavities 19 in odd-numbered stages counted from the bottom arearranged in parallel.

In the case of a first type fluid actuator in which the core 13 isexposed only at its upper portion and to which one kind of fluid flowpassage, i.e., the fluid flow passage 21 is connected as in the firstand second embodiments, an effective pressure-receiving area S isexpressed by the following equation:

S=n·A−(n−1)·a

Where

a is the effective pressure-receiving area of the small seal member 17;

A is the effective pressure-receiving area of the large seal member 18;and

n is the number of small cavities 19 where pressurized fluid flows inand out and which communicate with each other.

Furthermore, in the case of a second type fluid actuator in which thecore 13 is exposed only at its upper portion and to which two kinds offluid flow passage, i.e., the first fluid flow passage 21 a and thesecond fluid flow passage 21 b are connected as in the third and fourthembodiments, while the above equation applies likewise to the smallcavities 19 in odd-numbered stages counted from the bottom, theeffective pressure-receiving area S as to the small cavities 19 ineven-numbered stages counted from the bottom is expressed by thefollowing equation:

S=n·(A−a)

FIG. 5 shows a fluid actuator 1C of the first type according to a fifthembodiment of the present invention, and FIG. 6 shows a fluid actuator2C of the second type according to a sixth embodiment of the presentinvention. In FIGS. 5 and 6, parts common to the foregoing fluidactuators are designated by the same reference numerals and theirdescription is omitted.

In these fluid actuators 1C, 2C, an elastic member 34 is providedbetween the bottom face of the cylinder casing 16 or 31 and the discs 12opposed thereto. This elastic member 34 comprises, for example, anelastomer or rubber, or a spring or the like, but these are notlimitative. The elastic member 34 may also be formed in combination ofdifferent kinds of materials, or by stacking these members.

Thus, in the above fluid actuator 1A or 2A, the elastic member 34 isincorporated in parallel to the fluid actuator 1A or 2A, i.e., so as torestrain the drive by the fluid actuator 1A or 2A, so that a force canact on a driven member with a spring constant larger than that of thefluid actuator 1A or 2A.

Like the fluid actuators 1C and 2C shown in FIGS. 5 and 6, the elasticmember 34 can be applied to the fluid actuator 1B shown in FIG. 2 andthe fluid actuator 2B shown in FIG. 4. The present invention alsoincludes other fluid actuators of the first and second types to whichthis elastic member 34 is applied.

FIG. 7 shows an application example of the fluid actuator 1A.

Referring to the figure, reference numeral 51 denotes a driven member,and this driven member 51 comprises a surface plate 51 a and a vibrationcontrolled object 51 b placed thereon such as a precision device.Further, in this figure, the driven member 51 is supported by four fluidactuators 1A, and conditions of movement such as velocity andacceleration of the driven member 51 are detected by a single sensor 52.However, as the controlled object of a rigid body system has six degreesof freedom, at least six sensors and six actuators are required forcontrolling the controlled object for all of the degrees of freedom.Generally, since the installation sites are limited in spite of anattempt to fulfill the control at this minimum number, the control isperformed by disposing at four corners of a rectangular shape eightactuators in total.

Accordingly, also in the case of the application example shown in FIG.7, in addition to the fluid actuators 1A shown in the figure, forexample, two fluid actuators 1A are placed in contact with a rectangularface of the surface plate 51 a illustrated in FIG. 7 and with anotherface(not shown) of the surface plate 51 a parallel to the aboveillustrated face. Further, in addition to the shown sensor 52, at leastfive sensors are provided. By these six sensors including the sensor 52,position, angle, velocity and acceleration of the driven member 51 orpressure of pressurized fluid within the fluid actuator 1A and the likeare detected depending on the purpose of the control. In general, when asignal derived from this sensor 52 represents a displacement, the signalis used for position and attitude control of the driven member 51, andwhen the signal represents an acceleration, the signal is used forvibration control.

Detection signals are inputted from the sensor 52 and the other fivesensors to a controller 53, and based on these detection signals, acontrol signal is outputted from the controller 53 to a control valve23, such as a servo valve, provided for each fluid actuator 1A. Thisservo valve, which itself is well known, has input port, output port andcontrol port which are not shown. Further, the input port is connectedto a pressurized fluid supply source 55, the control port is connectedto the fluid flow passage 21 so as to communicate with the small cavity19 in the first-numbered stage, and the output port is opened to theatmosphere. Thus, the control valves 23 are actuated in response to avoltage signal which is a control signal outputted from the controller53, so that a control force proportional to this voltage is generated inthe small cavities 19 via the fluid supplied from the pressurized fluidsupply source 55. It is needless to say that this pressurized fluid issupplied to the small cavities 19 in one case, and discharged from thesmall cavities 19 in another case.

In this way, the control for the fluid actuators 1A is performed, andaction of the driving force on the driven member 51 according to thepurpose can be obtained. For example, vibration removing or position andattitude control or the like on the driven member 51 is performed.

The control valves 23, without being limited to electrical type, may bemechanical type, one example of which is disclosed in JP A H3-219141.The control valve described in this publication JP A H3-219141 is amechanical three-way switching valve which is actuated by a lever, andwhich performs position control of the surface plate of a vibrationremoving table using an air spring. In more detail, while an end portionof the lever is kept in contact with the surface plate to monitor theposition of the surface plate, supply and discharge of the fluid isperformed by the control valve in correspondence to a displacement of aplunger of the control valve from its original position so that theplunger is slid through an amount proportional to a displacement amountof the surface plate.

Needless to say, another fluid actuator of the first or second type maybe applied instead of the fluid actuator 1A in FIG. 7.

When a fluid actuator of the second type is applied instead of the fluidactuator 1A in FIG. 7, it may be arranged that a control valveinterveniently provided on the first fluid flow passage 21 acommunicating with the small cavities 19 in odd-numbered stages, as wellas another control valve interveniently provided on the second fluidflow passage 21 b communicating with the small cavities 19 ineven-numbered stages are controlled by a single controller 53. However,for the second type fluid actuators such as the fluid actuator 2A, 2B or2C, it is not necessarily required that the fluid actuators be placed onboth sides of the driven member 51 in an opposing arrangement as shownin FIG. 7.

That is, as shown in FIG. 8, with respect to two opposing faces of thedriven member 51, the output shaft 11 of the fluid actuator of thesecond type, for example, the fluid actuators 2A may be fixed to oneface of the driven member 51, in which case a control force can beoperated on the driven member 51 similarly. Whereas the fluid actuators1A, 1B and 1C need to be placed oppositely on both sides of the drivenmember 51 so as to maintain the static pressure balance, the fluidactuators 2A may be placed on either one surface out of the opposingsurfaces for maintaining the static pressure balance. This is the casealso with the fluid actuators 2B and 2C.

Meanwhile, in the above described application examples, a signal fromone sensor may be used for the control of a plurality of control valves,and conversely, signals from a plurality of sensors may be used for thecontrol of one control valve.

In addition, when a fluid actuator according to the present invention isapplied to a driven member, it is preferable that a force from thedriven member does not act on the output shaft of the fluid actuator asa shearing force in a direction perpendicular to the longitudinaldirection of the output shaft. That is, it is desirable that a member ora mechanism for letting the shearing force escape be providedinterveniently between the output shaft and the driven member or thatthe output shaft itself be formed so as to absorb the shearing force. Amember that acts to conduct the longitudinal force and absorb theshearing force is already known, and such a member is exemplified by awire or a laminate of metallic plate and rubber as disclosed in theaforementioned publication JP A H3-219141.

Subsequently, a hybrid actuator using the above-described fluidactuators according to the present invention is described.

FIG. 9 shows an application example of a hybrid actuator 61A using theabove-described fluid actuator 1A. This hybrid actuator 61A comprisesthe fluid actuator 1A and a vibration actuator 71 arranged in series.Whereas this order of placement is not limitative, the vibrationactuator 71 is provided between the fluid actuator 1A and the drivenmember 51 in the case of the hybrid actuator 61A shown in the FIG. 9.

A fluid flow passage 21 connected to the fluid actuator 1A extends froma pressurized fluid supply source 55, and a control valve 23 a providedon the fluid flow passage 21 is an electrically driven servo valvehaving good responsibility. In the following description, the fluid fromthe pressurized fluid supply source 55 is assumed to be gas as anexample.

This control valve 23 a is an electromagnetic three-way valve having asupply port communicating with the pressurized fluid supply source 55, acontrol port communicating with the small cavity 19, and a dischargeport communicating with the atmosphere. This control valve 23 a servesto adjust the flow rate of pressurized gas introduced from thepressurized fluid supply source 55 to the small cavity 19 as well as theflow rate of gas discharged from the small cavity 19. When the controlvalve 23 a is in a first state in which the flow rate of thispressurized gas is at a maximum, the discs 12 operate so as to expandthe small cavities 19 by the pressure of the pressurized gas introducedfrom the pressurized fluid supply source 55 to the small cavities 19. Onthe other hand, when the control valve 23 a is in a second state inwhich the discharge flow rate of the pressurized gas is at a maximum,the gas in the small cavities 19 flows out, so that the action of thegas pressure is weakened, causing the discs 12 to operate in a directionopposite to that of the first state.

The term vibration actuator 71 is meant to include a solid elementactuator containing a solid element such as a piezoelectric-elementwhich yields strain with a voltage applied or an ultra-magnetostrictionelement which yields strain under the action of a magnetic field, andbesides a linear motor such as a voice coil motor (VCM). In addition tothe operation of the fluid actuator 1A, this vibration actuator 71expands and contracts up and down, thereby causing an upward or downwardforce to act on the driven member 51.

The driven member 51 is provided with a vibration sensor 72 fordetecting vibration state of the driven member 51 in the verticaldirection, and a detection signal showing the vibration state isinputted from this vibration sensor 72 to a controller 73. Further, thefluid actuator 1A is provided with a displacement sensor 74 fordetecting vertical relative displacement of the driven member 51 withrespect to the fluid actuator 1A, and a detection signal from thisdisplacement sensor 74 is inputted to the controller 73. Based on thesedetection signals, a control signal is fed from the controller 73 to adriver 75 serving as both an actuator driver and a valve driver, and thevibration actuator 71 is actuated by this driver 75. Furthermore, airflow in the control port of the control valve 23 a is controlled by thisdriver 75.

Meanwhile, the displacement sensor 74 may also be provided on the drivenmember 51 instead of the fluid actuator 1A, in which case relativedisplacement of the fluid actuator 1A with respect to the driven member51 is detected by this displacement sensor 74.

More specifically, in the controller 73, an input signal is divided intohigh-frequency components and low-frequency components, and a controlsignal based on these high-frequency components is inputted to avibration-actuator driver section of the driver 75, while a controlsignal based on the low-frequency components is inputted to avalve-driver section of the driver 75. The vibration-actuator driversection is connected to the vibration actuator 71, and the valve-driversection is connected to a valve-body driver portion of the control valve23 a. Thus, on the driven member 51, a driving force of high frequenciesis effected by the vibration actuator 71, while a driving force of lowfrequencies is effected by the fluid actuator 1A.

As described above, in this hybrid actuator 61A, vibration control isdividedly allotted to the fluid actuator 1A and the vibration actuator71, respectively, where the vibration signal from the driven member 51is fed back not only to the vibration actuator 71 but also to thecontrol valve 23 a that controls the drive of the fluid actuator 1A. Asa matter of course, without limitations to signals on the driven member51, a ground motion signal detected from the installation site of thehybrid actuator 61A, for example, the floor surface may also be inputtedto the controller 73 and, by using this ground motion signal in additionto the aforementioned signal, feed-forward control may be performed.That is, the method of simultaneous drive is not limitative. In thiscase, operation signals matching dynamic characteristics of thevibration actuator 71 and dynamic characteristics of the fluid actuator1A, respectively, may be separated and generated by the controller 73.Since the method for this generation is not a principal point of thepresent patent application, this method is omitted in description.However, it has commonly been performed to change control gain accordingto the band based on differences in stroke and differences in responsecharacteristics.

In the hybrid actuator 61A shown in FIG. 9, another fluid actuator ofthe first type may be applied instead of the fluid actuator 1A.

In addition, it is not necessarily required to separate high-frequencycomponents and low-frequency components of the input signal in thecontroller 73. For example, a prefilter matching the dynamiccharacteristics (e.g., proportional type, integral type, derivativetype) of the vibration actuator 71 and/or the fluid actuator 1A may beinterveniently provided on the secondary side of the controller 73 sothat a signal matching the vibration actuator 71 and/or the fluidactuator 1A is generated via this prefilter from a signal derived fromthe controller 73. As a result, the controller 73 only needs to outputone kind of signal based on a signal from the vibration sensor 72.

FIG. 10 shows an application example of a hybrid actuator 62A using thefluid actuator 2A. In FIG. 10, parts in common to those shown in FIG. 9are designated by the same reference numerals and their description isomitted.

This hybrid actuator 62A is the same as the hybrid actuator 61A, exceptthat control valves 23 a of the first fluid flow passage 21 a and thesecond fluid flow passage 21 b are controlled by the driver 75, thusallowing upward and downward bidirectional forces to positively act uponthe driven member 51.

In the hybrid actuator 62A shown in FIG. 10, another fluid actuator ofthe second type may be applied instead of the fluid actuator 2A.

Further, in the application examples shown in FIGS. 7 to 10, an elasticmember may be provided interveniently in series to the fluid actuator,where the order of arrangement of the elastic member and the fluidactuator is not limitative.

FIG. 11 shows an application example of a hybrid actuator 61B using afluid actuator 1D which is substantially identical with the foregoingfirst embodiment. This hybrid actuator 61B comprises a fluid actuator1D, an elastic member 76 and a vibration actuator 71 arranged in seriesto one another.

The fluid actuator 1D, like the fluid actuator 1A, comprises a cylindercasing 16, discs 12 disposed opposite to the bottom face of the cylindercasing 16, and a small seal member 17 and a large seal member 18 whichsupport the discs 12 so as to be operable in such a manner that opposingfaces of the cylinder casing 16 and the discs 12 go closer to or fartherfrom each other, and which form closed spaces, i.e. small cavities 19,together with the cylinder casing 16 and the discs 12. In addition, afluid flow passage 21 whose one end communicates with, for example, thelowermost small cavity 19 extends from the pressurized fluid supplysource 55, and this fluid flow passage 21 has a control valve 23 bprovided thereon. Further, in this fluid actuator 1D, the small cavity19 in the first-numbered stage and the small cavity 19 in thethird-numbered stage communicate with each other by means of a throughhole 33 formed in the cylinder casing 16. The small cavity 19 in thesecond-numbered stage communicates with the atmosphere via a throughhole 22.

The elastic member 76 is made of, for example, elastomer, rubber, springor the like, but not limited to these. The elastic member 76 may also beformed by combining different kinds of members or laminating thosemembers.

The control valve 23 b is a three-way switching valve of the mechanicaldrive type having a supply port, a control port and a discharge portsimilar to those of the control valve 23 a. By this control valve 23 b,the flow rate of the pressurized gas introduced from the pressurizedfluid supply source 55 to the small cavities 19 as well as the flow rateof the gas discharged from the small cavities 19 are controlled. Then,if the control valve 23 b is in the first state in which the supply flowrate of this pressurized gas is maximized, the discs 12 are actuated bythe pressure of the pressurized gas introduced from the pressurizedfluid supply source 55 to the small cavities 19 in such a direction thatthe aforementioned opposing surfaces are separated farther away. On theother hand, if the control valve 23 b is in the second state in whichthe discharge flow rate of the pressurized gas is maximized, the gas inthe small cavities 19 goes out, weakening the action of the gaspressure, so that the discs 12 are actuated in a direction opposite tothat of the first state.

The driven member 51 is provided with a vibration sensor 72 fordetecting vertical vibration state of the driven member 51. A detectionsignal showing a vibration state is inputted from this vibration sensor72 to an actuator controller 77, and a control signal is fed from theactuator controller 77 to an actuator driver 78 based on the inputteddetection signal, so that the vibration actuator 71 is driven by theactuator driver 78.

Further, a position sensing lever 79 is provided on the cylinder casing16. One end of this position sensing lever 79 is in contact with thedriven member 51 so as to operate up and down integrally therewith,thereby causing the valve body of the control valve 23 b to move throughan amount proportional to an amount of displacement of the driven member51. Thus, the flow of gas at the control port is controlled.

The order of arrangement of the fluid actuator 1D, the elastic member 76and the vibration actuator 71 is not limited, and the fluid actuator 1Dor the elastic member 76 may be arranged in contact with the drivenmember 51.

In addition, the position sensing lever 79 may also be provided on thedriven member 51 instead of the cylinder casing 16, so that relativedisplacement of the cylinder casing 16 to the driven member 51 isdetected.

FIG. 12 shows an application example of another hybrid actuator 61Cusing the fluid actuator 1D shown in FIG. 11, where parts common to theforegoing hybrid actuators are designated by the same reference numeralsand the description is omitted.

This hybrid actuator 61C comprises the above-described control valve 23a which is an electromagnetic type three-way switching valve having asupply port, a control port and a discharge port, a displacement sensor74 which is provided on the cylinder casing 16 and which detectsvertical relative displacement of the driven member 51 with respect tothe cylinder casing 16 in a non-contact manner, a valve controller 81for, upon receiving an electric signal showing a displacement state fromthe displacement sensor 74, outputting a control signal based on theelectric signal, and a valve driver 82 for actuating the control valve23 a upon receiving this control signal. Then, by this control valve 23a, the flow of air at the control port is controlled like the abovecase. Also, as in the above case, the displacement sensor 74 may beprovided on the driven member 51 instead of the cylinder casing 16.

This hybrid actuator 61C is one in which the position control functionof the fluid actuator 1D is positively enhanced as compared with thehybrid actuator 61B shown in FIG. 11. The hybrid actuator 61C is capableof measuring the position of the driven member 51, which is the objectof control, by the displacement sensor 74, and driving the control valve23 a based on an error from a target position to fulfill feedbackcontrol of the position or to fulfill feedforward control thereof basedon a target voltage, so that the position of the driven member 51 can becontrolled. Then, with the above constitution, the hybrid actuator 61Cbecomes capable of achieving such large strokes and heavy controlobjects as could not be attained by the vibration actuator 71 alone.Meanwhile, the displacement sensor 74 is a non-contact type gap sensor,but without being limited to this, may be a displacement sensor of othertypes.

FIG. 13 shows an application example of another hybrid actuator 61Dusing the fluid actuator 1D shown in FIG. 11, where parts common to theforegoing fluid actuators are designated by the same reference numeralsand their description is omitted.

In this hybrid actuator 61D, detection signals by the vibration sensor72, and the displacement sensor 74 are inputted to the controller 73,and based on these detection signals, the vibration actuator 71 and thecontrol valve 23 a are controlled via the driver 75 by the controller73.

FIG. 14 shows an application example of another hybrid actuator 61Eusing the fluid actuator 1D shown in FIG. 11, where parts common to theforegoing fluid actuators are designated by the same reference numeralsand their description is omitted.

In this hybrid actuator 61E, an elastic member 34 is provided betweenthe cylinder casing 16 of the fluid actuator 1D and the lowermost disc12 in the same manner as the embodiments shown in FIGS. 5 and 6.

Thus, by incorporating the elastic member 34 into the fluid actuator 1Din parallel to the fluid actuator 1D, i.e., in such a way that the driveby the fluid actuator 1D is restricted, it become possible to supportthe vibration actuator 71 with a spring constant larger than that of thefluid actuator 1D alone.

In the case of a conventional vertical actuator for vibration removingwhich is so designed that all loads are supported by the vibrationactuator and the elastic member, it could be assumed that the elasticmember such as elastomer would wear out by long-term support, beingplastically deformed, so that the driven member would be changed inposition. On the other hand, the hybrid actuator 61E is capable ofstrictly maintaining the position of the driven member by compensatingthe amount of plastic deformation of the elastic member 34 with thepressure of the fluid actuator 1D, and besides the hybrid actuator 61Ecan easily compensate fluctuations of loads.

Needless to say, the internal pressure of the fluid actuator 1D iscontrolled and used for vibration suppression, as in the case of thehybrid actuator 61D. However, the effective pressure-receiving area ofthe hybrid actuator 61E is reduced and, the internal pressure of thefluid actuator 1D is lowered due to reduction of the load shared by thefluid actuator 1D by the elastic member 34 disposed in the hybridactuator 61E, thus resulting in smaller control force.

Meanwhile, in the hybrid actuators shown in FIGS. 9 to 14, it ispreferable that the thickness of the small cavities 19 of the fluidactuator be several tens to hundreds μm, thereby increasing the springconstant of the fluid actuator.

FIG. 15 shows an application example of a hybrid actuator 62B using afluid actuator 2D substantially identical with the foregoing thirdembodiment except for the number of the small cavities 19, where partscommon to the foregoing hybrid actuators are designated by the samereference numerals and their description is omitted.

This hybrid actuator 62B comprises a fluid actuator 2D and a vibrationactuator 71 arranged in series. An annular protrusion 15 is formedinside an upper end portion of the fluid actuator 2D, and the fluidactuator 2D is so formed as to have a portion, that is, a projectingportion 84 in the illustrated example, which is exposed from a centralportion of upper pressure-receiving surface 83 that receives a forceoppositely directed to the force received from the small cavity 19 underthe disc 12, to the space above the annular protrusion 15 via the smallseal member 17. Meanwhile, this exposed portion does not necessarilyneed to be projecting from the upper pressure-receiving surface 83, andmay be a part of the flat top surface of the upper pressure-receivingsurface 83.

The fluid flow passage 21 is branched into a first fluid flow passage 21a and a second fluid flow passage 21 b, and the first fluid flow passage21 a and the second fluid flow passage 21 b communicate with smallcavities 19 via control valves 23 a, respectively, independently of eachother.

Further, detection signals outputted from the vibration sensor 72 andthe displacement sensor 74 are inputted to the controller 73, and basedon these detection signals, the vibration actuator 71 and the twocontrol valves 23 a are controlled via the driver 75 by the controller77. Accordingly, internal pressures of the two small cavities 19 arecontrolled independently of each other.

This hybrid actuator 62B is designed so as to be able to solve theproblem of reduced driving force of the hybrid actuator 61E and to setapart the issues of position control and vibration control from eachother. Since the small cavity 19 in the first-numbered stage and thespace 19 in the second-numbered stage serving as opposing drivers of thefluid actuator 2D are formed independently of each other, pressuredifference between the small cavities contributes to positional change,making it possible to infinitely reduce the share of load due to thefluid pressure within the fluid actuator 2D. That is, load is imposed onthe elastic member 34 so that the disc 12 receives equal force at upperand lower surfaces from the fluid, by which load imposed on the fluidactuator 2D can be eliminated. Therefore, the positional change of thedriven member 51 between a case in which the fluid pressure is naughtand another case in which the fluid pressure is applied can be madeinfinitely close to zero. As a result, in applications for vibrationremoving, there can be obtained an advantage that the load condition ofthe fluid actuator 2D does not change between its de-energization andits energization.

FIG. 16 shows an application example of a further hybrid actuator 62Cusing the fluid actuator 2D shown in FIG. 15, where parts common to theforegoing fluid actuators are designated by the same reference numeralsand their description is omitted.

In this hybrid actuator 62C, the vibration actuator 71 has a solidelement or linear motor that operates laterally, and is pressed fromopposite sides by two elastic members 85 disposed on opposite sides atall times. Also, in the example shown in FIG. 16, between the drivenmember 51 and the vibration actuator 71, a sensor unit 86 isinterveniently provided which comprises a vibration sensor for detectingvertical vibration state, a vibration sensor for detecting horizontalvibration state. Furthermore, the sensor unit 86 may be a displacementsensor for detecting horizontal displacement in accordance with controlcontent.

Thus, detection signals from the each sensor are inputted to thecontroller 73 and, based on these detection signals, the vibrationactuator 71 and the two control valves 23 a are controlled from thecontroller 73 via the driver 75. In addition, in this case, the solidelement that operates vertically and the solid element or linear motorthat operates horizontally in the vibration actuator 71 are controlledindependently of each other.

Meanwhile, the aforementioned fluid actuator may be used instead of theelastic members 85 so as to allow the drive in directions of X-axis andY-axis, which are perpendicular to each other, and further in adirection of Z-axis.

FIG. 17 shows an application example of another hybrid actuator 62Dusing the foregoing fluid actuator 2D, where parts common to theforegoing fluid actuator are designated by the same reference numeralsand their description is omitted.

In this hybrid actuator 62D, a ground motion sensor unit 87 fordetecting vertical vibration of the installation site of the hybridactuator 62D, for example, the floor surface is provided intervenientlybetween the installation site and the fluid actuator 2D, so that aground motion signal detected by this ground motion sensor unit 87 isinputted to the controller 73 and that the vibration actuator 71 and thetwo control valves 23 a are controlled via the driver 75 based onsignals from the displacement sensor 74, the sensor unit 86 and theground motion sensor unit 87.

FIG. 18 shows an application example of another hybrid actuator 62Eusing the fluid actuator 2D shown in FIG. 15, where parts common to theforegoing hybrid actuator are designated by the same reference numeralsand their description is omitted.

In this hybrid actuator 62E, an elastic support member 88 and anadditional mass 89 arranged in series are provided intervenientlybetween the vibration actuator 71 and the driven member 51. Thus,detection signals by the displacement sensor 74 and various sensorsaccommodated in the sensor unit 86 are inputted to the controller 73,and based on these signals, the vibration actuator 71 and the twocontrol valve 23 a are controlled via the driver 75.

This hybrid actuator 62E is an application to a doublevibration-proofing system. By virtue of using the additional mass 89,the hybrid actuator 62E is improved in vibration isolationcharacteristic of high frequency region without yielding resonancepoints in low frequency region.

The present invention also includes hybrid actuators in which thevibration actuator is placed below and the fluid actuator is placedabove the vibration actuator.

Also, the above-described elastic member 34 does not necessarily need tobe provided.

Next, a fluid actuator of a third type which has upper and lowerportions of the core exposed and which is connected to one kind of fluidflow passage, as well as a fluid actuator of a fourth type in whichupper and lower portions of the core are exposed and which is connectedto two kinds of fluid flow passages are described.

FIG. 19 shows a fluid actuator 3A according to a seventh embodiment ofthe invention as well as an application example thereof, where partscommon to the foregoing fluid actuators are designated by the samereference numerals and their description is omitted.

This fluid actuator 3A comprises a cylinder casing 91 opened at upperand lower portions and placed on a support portion X, and a core 92placed inside the cylinder casing 91 and supporting a driven member 51.

A single annular protrusion 15 is projecting laterally at innerperiphery of the cylinder casing 91, and a single disc 12 is projectinglaterally at outer periphery of the core 92. A small seal member 17 isinterposed between the annular protrusion 15 and the core 92 withoutinterfering with upward and downward relative movement of these twomembers, and a large seal member 18 is interposed between the disc 12and the inner periphery of the cylinder casing 91.

A small cavity 19 is formed between the small seal member 17 and thelarge seal member 18 so that the effective pressure-receiving area ofthis small cavity 19 on the large seal member 18 side is larger than itseffective pressure-receiving area on the small seal member 17 side. Inaddition, a fluid flow passage 21 having a control valve 23 ainterveniently provided thereon is connected to the cylinder casing 91,so that a pressurized fluid, for example, a gas is supplied to the smallcavity 19 while gas within the small cavity 19 is discharged.

For the small seal member 17 and large seal member 18, for example,diaphragms comprising annular thin plates or O-rings are used as in theabove case.

To the driven member 51 on the core 92 is attached a vibration sensor 72for detecting vibration state of the driven member 51. A detectionsignal showing the vibration state by the vibration sensor 72 isoutputted to a valve controller 81, and a control signal is outputtedfrom this valve controller 81 to a valve driver 82 that actuates thecontrol valve 23 a.

FIG. 20 shows a fluid actuator 3B according to an eighth embodiment ofthe invention as well as an application example thereof, where partscommon to the foregoing fluid actuator are designated by the samereference numerals and their description is omitted.

In this fluid actuator 3B, the cylinder casing 91 of the fluid actuator3B is fixed to a support portion X located above, and the driven member51 is hung down on a lower end of the core 92.

FIG. 21 shows a fluid actuator 3C according to a ninth embodiment of theinvention as well as an application example thereof, where parts commonto the foregoing fluid actuators are designated by the same referencenumerals and their description is omitted.

In this fluid actuator 3C, a small cavity 19 communicating with theatmosphere by means of a through hole 22 is provided between the twosmall cavities 19. The two small cavities 19 communicate with each otherby means of a through hole 34 connected to the fluid flow passage 21.

FIG. 22 shows a fluid actuator 3D according to a tenth embodiment of theinvention as well as an application example thereof, where parts commonto the foregoing fluid actuators are designated by the referencenumerals and their description is omitted.

This fluid actuator 3D has the small cavities 19 in first-numbered stageand third-numbered stage communicating with each other by means of athrough hole 22, and the small cavities 19 in second-numbered stage andfourth-numbered stage communicating with each other by means of athrough hole 34. The through hole 22 communicates with the atmosphere,and the through hole 34 is connected to the fluid flow passage 21.

FIG. 23 shows a fluid actuator 4A according to an eleventh embodiment ofthe invention as well as an application example thereof, where partscommon to the foregoing fluid actuators are designated by the samereference numerals and their description is omitted.

This fluid actuator 4A has a small seal member 17 between an annularprotrusion 15 and a core 94 within a cylinder casing 93 opened at upperand lower portions, as well as a large seal member 18 between a disc 12projected from the core 94 and the inner periphery of the cylindercasing 93. Further, two small cavities 19 are formed above and below thesmall seal member 17, one of the small cavities 19 communicating with afirst fluid flow passage 21 a and the other communicating with a secondfluid flow passage 21 b.

FIG. 24 shows a fluid actuator 4B according to a twelfth embodiment ofthe invention as well as an application example thereof, where partscommon to the foregoing fluid actuators are designated by the samereference numerals and their description is omitted.

This fluid actuator 4B has the small cavities 19 in first-numbered stageand third-numbered stage communicating with each other by means of athrough hole 22, and the small cavities 19 in second-numbered stage andfourth-numbered stage communicating with each other by means of athrough hole 34. The through hole 34 is connected to the first fluidflow passage 21 a and the through hole 22 is connected to the secondfluid flow passage 21 b.

In the application examples of the fluid actuators shown in FIGS. 19 to24, an elastic member may be interveniently provided above or below thecore 92 or 94, and an elastic member may be interveniently providedbelow the cylinder casing 91 or 93.

FIG. 25 shows a hybrid actuator 63A using the fluid actuator 3A as wellas an application example thereof, where parts common to the foregoingembodiments are designated by the same reference numerals and theirdescription is omitted.

This hybrid actuator 63A generally comprises the core 92 of the fluidactuator 3A, the vibration actuator 71 and the elastic member 76arranged in series, where the cylinder casing 91 and the vibrationactuator 71 are supported on a support portion X.

To the driven member 51 placed on the core 92 of the fluid actuator 3Ais attached a vibration sensor 72 for detecting vibration state of thedriven member 51. A detection signal showing the vibration state by thevibration sensor 72 is inputted to a valve controller 81, and a controlsignal is outputted from this valve controller 81 to a valve driver 82that actuates the control valve 23 a. A detection signal from thevibration sensor 72 is inputted also to the actuator controller 77, fromwhich a control signal is sent to the actuator driver 78, so that thevibration actuator 71 is driven up and down by the actuator driver 78.

Meanwhile, in the case where this hybrid actuator 63A is used upsidedown with respect to the state of the FIG. 25, i.e., where the supportportion X is located above while the fluid actuator 3A and the vibrationactuator 71 are hung down on the support portion X, the disc 12 and theannular protrusion 15 has to be formed in such a way that the large sealmember 18 is located above while the small seal member 17 is locatedbelow in order that upward force acts on the core 92.

FIG. 26 shows a hybrid actuator 63B using the fluid actuator 3A as wellas an application example thereof, where parts common to the foregoingembodiments are designated by the same reference numerals and theirdescription is omitted.

This hybrid actuator 63B generally comprises the cylinder casing 91 ofthe fluid actuator 3A, the vibration actuator 71 and the elastic member76 arranged in series, where the core 92 and the vibration actuator 71are supported on a support portion X.

The vibration actuator 71 and the elastic member 76 are, preferably,shaped cylindrically, but not limited to the shape.

FIG. 27 shows a hybrid actuator 63C using the fluid actuator 3A as wellas an application example thereof, where parts common to the foregoingembodiments are designated by the same reference numerals and theirdescription is omitted.

This hybrid actuator 63C generally comprises the core 92 of the fluidactuator 3A, the vibration actuator 71 and the elastic member 76arranged in series, where the cylinder casing 91 and the vibrationactuator 71 are supported on a support portion X.

Thus, the elastic member 76 does not necessarily need to be provided atone place, and may be provided at a plurality of places, and besides theelastic member 76 may be provided interveniently between the supportportion X and the vibration actuator 71.

FIG. 28 shows a fluid actuator 3E according to a thirteenth embodimentof the invention as well as an application example of a hybrid actuator63D using the fluid actuator 3E, where parts common to the foregoingembodiments are designated by the same reference numerals and theirdescription is omitted.

This hybrid actuator 63D generally comprises the core 92 of the fluidactuator 3E, the elastic member 76 and the vibration actuator 71arranged in series, where the cylinder casing 91 and the vibrationactuator 71 are supported on a support portion X.

The fluid actuator 3E has the small cavities 19 in first-numbered stageand third-numbered stage communicating with each other by means of athrough hole 20 formed in the core 92, and the small cavity 19 insecond-numbered stage communicating with the atmosphere by means of athrough hole 22 formed in the cylinder casing 91. The small cavity 19 infirst-numbered stage communicates also with the fluid flow passage 21.

FIG. 29 shows a fluid actuator 4C according to a fourteenth embodimentof the invention as well as an application example of a hybrid actuator64A using the fluid actuator 4C, where parts common to the foregoingembodiments are designated by the same reference numerals and theirdescription is omitted.

This hybrid actuator 64A generally comprises the core 94 of the fluidactuator 4C, the elastic member 76 and the vibration actuator 71arranged in series, where the cylinder casing 93 and the vibrationactuator 71 are supported on a support portion X.

The fluid actuator 4C has two small cavities 19, one communicating withthe first fluid flow passage 21 a and the other communicating with thesecond fluid flow passage 21 b.

FIG. 30 shows a fluid actuator 4D according to a fifteenth embodiment ofthe invention as well as an application example of a hybrid actuator 64Busing the fluid actuator 4D, where parts common to the foregoingembodiments are designated by the same reference numerals and theirdescription is omitted.

This hybrid actuator 64A generally comprises the core 92 of the fluidactuator 4D, the elastic member 76 and the vibration actuator 71arranged in series, where the cylinder casing 93 and the vibrationactuator 71 are supported on a support portion X.

The fluid actuator 4D has the small cavities 19 in first-numbered stageand third-numbered stage communicating with each other by means of athrough hole 20, and the small cavities 19 in second-numbered stage andfourth-numbered stage communicating with each other by means of athrough hole 22. The through hole 20 is connected to the first fluidflow passage 21 a and the through hole 22 is connected to the secondfluid flow passage 21 b.

In the application examples of the hybrid actuators shown in FIGS. 25 to30, the elastic member may be interveniently provided above below thecore 92, 94, and the elastic member may also be interveniently providedbelow the cylinder casing 91, 93.

Whereas the vertical direction herein refers to a direction on theaccompanying drawings, it is needless to say that the above-describedfluid actuators and hybrid actuators may be placed so that force isgenerated in one direction only, or that force is generated indirections of X- and Y-axes perpendicular to each other, and besides ina direction of Z-axis. Accordingly, the above-described fluid actuatorsand hybrid actuators may be placed horizontally so that not onlyvertical but also horizontal forces are generated, so that forces act indirections of two-axes or three-axes, by which the driven member can becontrolled, for example, for position control or vibration control.

In the fluid actuators as described above, preferably, a plurality ofsupply ports for pressurized gas to the small cavities 19 are provideduniformly over the small cavities 19 in order that the pressurized gasis supplied generally uniformly from the fluid flow passage 21, thefirst fluid flow passage 21 a and the second fluid flow passage 21 b tothe small cavities 19 directly communicating with these fluid flowpassages, respectively.

Preferably, a reserve tank for storing pressurized gas is provided at aportion of the fluid flow passage 21 or portions of the first fluid flowpassage 21 a and the second fluid flow passage 21 b between the controlvalves 23, 23 a, 23 b and the small cavities 19 or on a flow passagecommunicating with the small cavities 19, so that the static springconstant of the fluid actuators becomes small. Further preferably,throttle means, for example, an orifice is provided at theaforementioned portion of the fluid flow passage 21, the first fluidflow passage 21 a and the second fluid flow passage 21 b or on the flowpassage that allow the small cavities 19 and the reserve tankcommunicated with each other.

In the present invention, the number of small cavities 19 is notlimited, and it is only required that the same kind of small cavities 19are not placed in adjacency, that is, different kinds of small cavities19 are arranged alternately.

The cylinder casing 16, 31, the annular protrusion 15 and the discs 12are each made of a member having enough rigidity for the discs 12 to beactuated in such a direction as to go apart from the annular protrusion15 when the pressurized gas is introduced into the small cavities 19.

The cylinder casing 16, 31 does do not necessarily need to be constantin inner diameter, and may also be formed into, for example, a truncatedconical shape. Furthermore, the disc 12 and the annular protrusion 15 ineach stages also do not need to be constant in inner diameter or outerdiameter.

In the present invention, the order of placement of the fluid actuator,the vibration actuator and the elastic member as described above is notlimitative, and the elastic member is not necessarily required. On thecontrary, a plurality of elastic members may be provided.

The core of the fluid actuator may be a hollow body.

As described hereinabove, the present invention allows applications tohigh loads with small space.

What is claimed is:
 1. A fluid actuator comprising: a single core havinga plurality of discs protruding around an output shaft; a cylindercasing which has a body hollow configuration with an opening provided atits upper portion, and which receives the core in the hollow body in astate where not only an upper end of the output shaft is projected outof the opening but a lower portion of the core is set free, and whichhas an annular protrusion projecting into an air gap between the discs;at least one friction-less, annular small diaphragm interposed between aportion of the core located between the discs and the annular protrusionso as to allow their relative movement in upward and downward directionsand so as to divide a space between the portion of the core and theannular protrusion into upper and lower portions; and a plurality offriction-less, annular large diaphragms each interposed between an innerperipheral surface of the cylinder casing and outer periphery portion ofthe disc so as to allow their relative movement in upward and downwarddirections and so as to allow their relative movement in upward anddownward directions and so as to divide a space between the innerperipheral surface of the cylinder casing and the outer peripheryportion of the disc into upper and lower portions; wherein a pluralityof small cavities are each interposed between neighboring ones of thesmall diaphragm and the large diaphragms or between the lowest largediaphragm and a bottom portion of the cylinder casing so as to bearrayed in an axial direction of the core, a first group of the smallcavities in even-numbered stages counted from the bottom communicatewith the atmosphere and a second group of the cavities communicate withone another, at least one small-cavity of the second group communicateswith a fluid flow passage for supplying and discharging pressurizedfluid, and an effective pressure-receiving area on the large diaphragmside is larger than an effective pressure-receiving area on the smalldiaphragm side in each of the small cavities.
 2. A hybrid actuatorcomprising: the fluid actuator described in claim 1; and a vibrationactuator which is connected to the fluid actuator in series.
 3. A hybridactuator comprising: the fluid actuator described in claim 1; avibration actuator; and an elastic member which is connected to thefluid actuator and the vibration actuator to one another in series.
 4. Afluid actuator comprising: a single core having a plurality of discsprotruding around an output shaft; a cylinder casing which has a body ofhollow configuration with an opening provided at its upper portion, andwhich receives the core in the hollow body in a state where not only anupper end of the output shaft is projected out of the opening but alower portion of the core is set free, and which has an annularprotrusion projecting into an air gap between the discs; at least onefriction-less, annular small diaphragm interposed between a position ofthe core located between the discs and the annular protrusion so as toallow their relative movement in an upward and downward directions andso as to divide a space between the portion of the core and the annularprotrusion into upper and lower sides; and at least one friction-less,annular large diaphragm which is interposed in alternate relation withthe small diaphragm between the core and the cylinder casing and doesnot interfere with upward and downward relative movement of the core andthe cylinder casing and has an effective pressure-receiving area largerthan that of the small diaphragm; a first fluid flow passage forsupplying pressurized fluid to at least one small cavity interposedbetween neighboring ones of the small diaphragm and the large diaphragmor between the lowest large diaphragm and a bottom portion of thecylinder casing in an odd-numbered stage counted from a bottom, and fordischarging the fluid from this small cavity; and a second fluid flowpassage for supplying pressurized fluid to at least one small cavityinterposed between neighboring ones of the small diaphragm and the largediaphragm in even-numbered stage counted from the bottom, and fordischarging the fluid from this small cavity.
 5. A hybrid actuatorcomprising: the fluid actuator described in claim 4; and a vibrationactuator which is connected to the fluid actuator in series.
 6. A hybridactuator comprising: the fluid actuator described in claim 4; avibration actuator; and an elastic member which is connected to thefluid actuator and the vibration actuator to one another in series.
 7. Afluid actuator comprising: a single core disposed inside the cylindercasing; at least one friction-less, small diaphragm which is interposedbetween the cylinder casing and the core and does not interfere withupward and downward relative movement of the core and the cylindercasing and the core; a plurality of friction-less, large diaphragms,each of which is interposed in alternate relation with the smalldiaphragm between the core and the cylinder casing and does notinterfere with upward and downward relative movement of the core and thecylinder casing and has an effective pressure-receiving area larger thanthat of the small diaphragm; a fluid flow passage for supplyingpressurized fluid to small cavities interposed between neighboring onesof the small diaphragm and the large diaphragms or between a lowestlarge diaphragm and a bottom portion of the cylinder casing in anodd-numbered stage counted from a bottom, and for discharging the fluidfrom the small cavity; and an opening which allows at least one smallcavity interposed between neighboring ones of the small diaphragm andthe large diaphragms in even-numbered stage counted from the bottom tocommunicate with the atmosphere.
 8. A hybrid actuator comprising: thefluid actuator described in claim 7; and a vibration actuator which isconnected to the fluid actuator in series.
 9. A hybrid actuatorcomprising: the fluid actuator described in claim 7; a vibrationactuator; and an elastic member which is connected to the fluid actuatorand the vibration actuator to one another in series.
 10. A fluidactuator comprising: a cylinder casing-opened at its upper portion; asingle core disposed inside the cylinder casing; at least onefriction-less small diaphragm which is interposed between the cylindercasing and the core and does not interfere with upward and downwardrelative movement of the cylinder casing and the core; at least onefriction-less, large diaphragm which is interposed in alternate relationwith the small diaphragm between the core and the cylinder casing anddoes not interfere with upward and downward relative movement of thecore and the cylinder casing and has an effective pressure-receivingarea larger than that of the small diaphragm; a first fluid flow passagefor supplying pressurized fluid to at least one small cavity interposedbetween neighboring ones of the small diaphragm and the large diaphragmor between a lowest large diaphragm and a bottom portion of the cylindercasing in odd-numbered stage counted from a bottom, and for dischargingthe fluid from this small cavity; and a second fluid flow passage forsupplying pressurized fluid to at least one small cavity interposedbetween neighboring ones of the small diaphragm and the large diaphragmin even-numbered stage counted from the bottom, and for discharging thefluid from this small cavity.
 11. A hybrid actuator comprising: thefluid actuator described in claim 10; and a vibration actuator which isconnected to the fluid actuator in series.
 12. A hybrid actuatorcomprising: the fluid actuator described in claim 10; a vibrationactuator; and an elastic member which is connected to the fluid actuatorand the vibration actuator to one another in series.
 13. A fluidactuator comprising: a cylinder casing opened at its upper and lowerportions; a single core disposed inside the cylinder casing; a smallfriction-less diaphragm which is interposed between the cylinder casingand the core and does not interfere with upward and downward relativemovement of the cylinder casing and the core; a large friction-lessdiaphragm which is interposed between the core and the cylinder casingand does not interfere with upward and downward relative movement of thecore and the cylinder casing and has an effective pressure-receivingarea larger than that of the small diaphragm; and a fluid flow passagefor supplying pressurized fluid to a small cavity interposed between thesmall diaphragm and the large diaphragm and for discharging the fluidfrom this small cavity.
 14. A hybrid actuator comprising: the fluidactuator described in claim 13; and a vibration actuator which isconnected to the fluid actuator in series.
 15. A hybrid actuatorcomprising: the fluid actuator described in claim 13; a vibrationactuator; and an elastic member which is connected to the fluid actuatorand the vibration actuator to one another in series.
 16. A fluidactuator comprising: a cylinder casing opened at its upper and lowerportions; a single core disposed inside the cylinder casing; at leastone small friction-less diaphragm which is interposed between thecylinder casing and the core and does not interfere with upward anddownward relative movement of the cylinder casing and the core; aplurality of large friction-less diaphragms each of which is interposedin alternate relation with the small diaphragm between the core and thecylinder casing and does not interfere with upward and downward relativemovement of the core and the cylinder casing and has an effectivepressure-receiving area larger than that of the small diaphragm; a fluidflow passage for supplying pressurized fluid to a small cavityinterposed between neighboring ones of the small diaphragm and the largediaphragms in odd-numbered stage counted from a bottom, and fordischarging the fluid from this small cavity; and an opening whichallows a small cavity interposed between neighboring ones of the smalldiaphragm and the large diaphragms in even-numbered stage, tocommunicate with the atmosphere.
 17. A hybrid actuator comprising: thefluid actuator described in claim 16; and a vibration actuator which isconnected to the fluid actuator in series.
 18. A hybrid actuatorcomprising: the fluid actuator described in claim 16; a vibrationactuator; and an elastic member which is connected to the fluid actuatorand the vibration actuator to one another in series.
 19. A fluidactuator comprising: a cylinder casing opened at its upper and lowerportions; a single core disposed inside the cylinder casing; at leastone small friction-less diaphragm which is interposed between thecylinder casing and the core and does not interfere with upward anddownward relative movement of the cylinder casing and the core; aplurality of large friction-less diaphragms each of which is interposedin alternative relation with the small diaphragm between the core andthe cylinder casing and does not interfere with upward and downwardrelative movement of the core and the cylinder casing and has aneffective pressure-receiving area larger than that of the smalldiaphragm; a first fluid flow passage for supplying pressurized fluid toa small cavity interposed between neighboring ones of the smalldiaphragm and the large diaphragms in even-numbered stage, and fordischarging the fluid from this small cavity.
 20. A hybrid actuatorcomprising: the fluid actuator described in claim 19; and a vibrationactuator which is connected to the fluid actuator in series.
 21. Ahybrid actuator comprising: the fluid actuator described in claim 19; avibration actuator; and an elastic member which is connected to thefluid actuator and the vibration actuator to one another in series.